PT-RS Configuration Depending on Scheduling Parameters

ABSTRACT

A transmitting node for a Radio Access Network, the transmitting node being adapted for transmitting, based on one or more transmission parameters, of reference signaling, and/or signaling including reference signaling, wherein the reference signaling comprises phase tracking reference signaling, and the one or more transmission parameters comprise a Modulation and Coding Scheme, MCS. The disclosure also pertains to related devices and methods.

TECHNICAL FIELD

The present disclosure pertains to wireless communication technology, inparticular radio access technology (RAT) and/or a radio access network(RAN), which may be a 5G network, e.g. according to 3GPP/NR (New Radio).

BACKGROUND

The physical layer of NR (the 3GPP 5G mobile radio systems) is expectedto handle a vast number of different transmission scenarios bysupporting multiple transmission numerologies, variable datatransmission time intervals and early decoding for latency criticalapplications. These new scenarios impose a need for the physical layerto be even more flexible than the case when LTE was first designed. Inaddition to these new transmission scenarios, the physical layer of NRshould be able to handle different transmission characteristics in termsof large variations in SINR, Doppler, delay spreads and channelrichness.

In mobile radio systems, reference signals for coherent demodulation ofphysical layer control and data channels signals may be transmittedwithin an OFDM waveform. The reference signal (RS) is multiplexed withthe physical layer channels and mapped on the OFDM time-frequencyresource grid as configured by the network. In LTE downlink, thedemodulation can be based on either cell-specific RS (CRS) orUE-specific RS (e.g. DM-RS), the type of which to be used depends onconfigured transmission mode. The mapping of CRS on the time-frequencyresource grid follows from the transmit-antenna configuration togetherwith a cell-specific frequency shift, derived during initial access,whereas the DM-RS mapping depends on the number of MIMO-layers.

The UE-specifically configured DM-RS can be pre-coded in the same way asthe corresponding physical layer channels and dynamically adapt thenumber of MIMO-layers to the radio channel conditions. Hence, one DM-RSantenna port is used per spatial MIMO layer scheduled to the UE. Anantenna port is associated to a given RS pattern of resource elementsover a time and frequency region. Different antenna ports may map todifferent resource elements to provide orthogonality.

Each transmitted MIMO layer thus has one associated DM-RS antenna port,and, since the data transmitted in that layer is precoded with the sameprecoder as the associated DM-RS, it is said that the data istransmitted on the associated DM-RS antenna port. The receiver will usethe associated antenna port when demodulating the data of a layer.

It may be preferable if different antenna ports are orthogonal whentransmitted, as it gives better channel estimation performance at thereceiver. This can be achieved by separation in time and frequency(different resource elements) or by using a combination with orthogonalcover codes (OCC) across multiple resource elements in time orfrequency.

With DM-RS, LTE supports up to 8-MIMO layers in downlink by using OCC intime.

FIG. 1 exemplarily illustrates the mapping of CRS and DM-RS patterns.

Like LTE, NR will be using OFDM based waveforms with reference signalsand physical layer channels mapped on a time-frequency resource grid (inparticular, for DL, in UL a special form of OFDM may be used, SC-FDM).Reference signals to be used in NR for demodulation of physical layerchannels have not yet been specified but will primarily be based onUE-specifically configured DM-RS patterns that can support multipletransmission numerologies, variable data transmission time intervals andearly decoding for latency critical applications.

FIG. 2 shows DM-RS structures that have been discussed to meetrequirements of early decoding or for low Doppler/low UE mobility (e.g.,low relative speed). In this structure, the early transmission of DM-RSenables demodulation and decoding of data to start almost directly afterreceiving the second OFDM symbol in the slot.

SUMMARY

It is an object of this disclosure to provide approaches allowingimproved handling of reference signaling, in particular PT-RS. Theapproaches in some aspects may facilitate low overhead for configuringand/or adaptive correction for phase errors.

There is disclosed a transmitting node for a Radio Access Network, thetransmitting node being adapted for transmitting, based on one or moretransmission parameters, of reference signaling and/or signalingincluding reference signaling. The reference signaling comprises phasetracking reference signaling, and the one or more transmissionparameters comprise a Modulation and Coding Scheme, MCS.

Also, a method for operating a transmitting node in a Radio AccessNetwork, the method comprises transmitting, based on one or moretransmission parameters, of reference signaling and/or signalingincluding reference signaling. The reference signaling comprises phasetracking reference signaling, and the one or more transmissionparameters comprise a Modulation and Coding Scheme, MCS.

The one or more transmission parameters may pertain to transmission bythe transmitting node, e.g. according to a configuration, and/or to aspecific channel like a physical channel, e.g. a data channel like aPhysical Uplink Shared CHannel like PUSCH, or a Physical Downlink SharedChannel like PDSCH, or a control channel like a physical uplink ordownlink control channel like PUCCH or PDCCH.

Accordingly, no additional signaling is needed to indicate whetherand/or how the reference signaling is to be transmitted.

In general, the one or more transmission parameters may be configured orindicated with a control message, in particular a DCI message.Transmission of reference signaling like phase tracking referencesignaling may be based on a reference signaling configuration. Theconfiguration may be indicated by the control message, e.g. a MCSindication therein. A MCS indication may generally comprise an indicatoror index or pointer or value or bit field indicating a MCS type and/or aMCS to be used or used for transmission. A transmission parameter may beconfigured or scheduled, and may be considered a scheduling parameter.

The transmitting node may be a radio node, in particular a terminal or anetwork node. A receiving node receiving the reference signaling orassociated transmission may be complementary thereto a network node or aterminal.

In some cases, transmitting may be in downlink, and/or may beterminal-specific and/or beam-formed.

Phase tracking reference signaling may be on one or more subcarriers,e.g. associated to a carrier or carrier frequency. The one or moresubcarriers may be carriers for which also demodulation referencesignaling (DM-RS) is scheduled, e.g. for the same slot or subframe,and/or leading in time compared to the phase tracking referencesignaling.

There is also disclosed a program product comprising code executable bycontrol circuitry, the code causing the control circuitry to carry outand/or control a method as described herein.

Moreover, a carrier medium arrangement carrying and/or storing a programproduct as disclosed herein is described.

Alternative or additional approaches are also discussed in thefollowing.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are provided merely to illustrate concepts and approachesdescribed herein, and are not intended to limit their scope. Thedrawings comprise:

FIG. 1, showing an illustration of CRS and DM-RS patterns in LTE;

FIG. 2, showing possible DM-RS patterns in NR for supporting earlydecoding/low Doppler;

FIG. 3, showing phase noise induced errors at carrier frequency of 10and 60 GHz, for different modulation and coding schemes;

FIG. 4, showing addition of PT-RS at high carrier frequency in NR;

FIG. 5, showing MCS dependent PT-RS configuration;

FIG. 6, showing an exemplary flow diagram of a method for the two cases:A: reception; B: transmission.

FIG. 7, showing PT-RS enabled for high MCS only; depending on carrierfrequency F;

FIG. 8, showing “No PT-RS”, either referred to mapping data instead ofPT-RS or to muting (zero power) of the PT-RS resource elements;

FIG. 9, showing a PT-RS placement illustration; a) Distributed PT-RS, b)Localized PT-RS;

FIG. 10, showing a scenario with multiple radio circuits available, e.g.for MIMO;

FIG. 11, showing an exemplary radio node implemented as terminal or userequipment; and

FIG. 12, showing an exemplary radio node implemented as network nodelike an eNodeB or gNodeB.

DETAILED DESCRIPTION

In the following, approaches are described with a focus on NRtechnology. However, they are applicable to other systems as well.

In NR deployments at higher carrier frequencies, the radio link willexhibit some new properties compared to LTE which is deployed at muchlower carrier frequencies, than targeted in NR. One of the fundamentalchanges is that the phase noise induced problems increase with thecarrier frequency, which introduces a need for a new phase referencesignal PT-RS (Phase Tracking RS). Such signal can be used both formitigation of the phase noise induced common phase error, experiencedequally on all subcarriers within an OFDM symbol, and inter-carrierinterference (ICI) caused by the loss of orthogonality betweensubcarriers. The impact of phase noise is depicted in FIG. 3, where thelink throughput with and without phase noise is shown at carrierfrequencies of 10 and 60 GHZ, for different coding and modulationschemes. At 10 GHz, phase noise has a limited impact on performance,while at 60 GHz significant performance loss is observed whencommunicating with higher order constellations, such as 64QAM. Thefigure shows that the PT-RS signal, used for reducing the phase noiseimpact, is mainly beneficial at certain MCSs and carrier frequencies.

This PT-RS reference signal can be needed both in uplink and downlink.It is foreseen that this signal can be used for both fine carrierfrequency-synchronization, and phase noise compensation. This signal isassumed to present and needed only at high carrier frequencies, whilethe other properties of the DM-RS can remain somewhat unchanged. Anexample of adding PT-RS at high carrier frequencies is depicted in FIG.4.

Always adding an PT-RS at higher frequencies causes additional overhead,whereas semi-statically configuring the PT-RS causes the system to beless agile in adopting to changes in transmission conditions.Accordingly, it is suggested dynamically indicating the PT-RSconfiguration using, e.g., one or more scheduling parameters, such as anindication of the MCS or the number of scheduled MIMO layers. It isobserved that in some cases PT-RS can be absent, leading to negligibledemodulation performance degradation but reduced overhead, in summary animproved user data throughput.

The use of an adaptive PT-RS is very efficient as there is a directcorrespondence between the achieved SINR and the selected MCS, furtherthere is a direct correspondence between the need for CPE and SINR andused modulation scheme (e.g. QPSK, 16 QAM and 64-QAM). For example, ifthe MCS changes quickly due to a change in the number of co-scheduledusers, no re-configuration is needed of for the PT-RS. With the proposedsolution, adjusting the MCS due to the co-scheduling directly gives thecorrect configuration of PT-RS.

Moreover, when multiple MIMO layers are scheduled to the same UE, thenthe need for accurate channel estimate is higher and PT-RS is useful toassist the UE in performing inter-layer interference suppression.

Generally, there may be considered a transmitting node for a wirelesscommunication network and/or for a Radio Access Network. Thetransmitting node may be adapted for transmitting reference signaling,and/or signaling including reference signaling. Reference signaling mayin particular comprise or be phase tracking reference signaling likePT-RS. The transmitting and/or the reference signaling and/or areference signaling configuration of the reference signaling may bebased on one or more transmission parameters, e.g. of the transmittedsignaling, and/or be based on link adaptation used. The transmittingnode may comprise a correspondingly adapted transmitting circuitry usedfor such transmitting, and/or a correspondingly adapted transmittingmodule. Alternatively, or additionally, the transmitting node may beadapted for indicating, e.g., to a terminal, a reference signalingconfiguration, e.g. implicitly or explicitly. The node may comprise acorresponding indicating module, and/or transmitting circuitry may beused therefor. More alternatively or additionally, the transmitting nodemay be adapted for determining a reference signaling configuration to beused for transmission based on one or more transmission parameters. Thetransmitting node may comprise correspondingly adapted control circuitryand/or a determining module. Transmitting signaling (which may includereference signaling) and/or transmitting reference signaling may bebased on such configuration. The reference signaling configuration maypertain to reference signaling to be transmitted by the transmittingnode.

A method for operating a transmitting node for or in a wirelesscommunication network and/or a Radio Access Network may be considered.The method may comprise transmitting reference signaling, and/orsignaling including reference signaling. Reference signaling may inparticular comprise or be phase tracking reference signaling like PT-RS.The transmitting and/or the reference signaling and/or a referencesignaling configuration of the reference signaling may be based on oneor more transmission parameters, e.g. of the transmitted signaling,and/or be based on link adaptation used. Alternatively, or additionally,the method may comprise indicating, e.g., to a terminal, a referencesignaling configuration, e.g. implicitly or explicitly. Morealternatively or additionally, the method may comprise determining areference signaling configuration to be used for transmission based onone or more transmission parameters. The transmitting node may comprisecorrespondingly adapted control circuitry and/or a determining module.Transmitting signaling (which may include reference signaling) and/ortransmitting reference signaling may be based on such configuration. Thereference signaling configuration may pertain to reference signaling tobe transmitted by the transmitting node.

There may be considered a method for operating a receiving node in awireless communication network and/or a RAN. The method may comprisereceiving reference signaling, in particular PT reference signaling,based on a reference signaling configuration, which may be a PT-RSconfiguration. Alternatively, or additionally, the method may comprisedetermining a reference signaling configuration, in particular a PT-RSconfiguration. The reference signaling configuration may pertain toreference signaling to be received by the receiving node.

A receiving node for a wireless communication network and/or a RAN maybe considered. The receiving node may be adapted for receiving referencesignaling, in particular PT reference signaling, based on a referencesignaling configuration, which may be a PT-RS configuration. Thereceiving node may be adapted for using receiving circuitry (of thereceiving node) for such receiving, and/or may comprise a correspondingreceiving module. Alternatively, or additionally, the receiving node maybe adapted for determining a reference signaling configuration, inparticular a PT-RS configuration. The receiving node may be adapted forusing control circuitry (of the receiving node) for such determining,and/or comprise a corresponding determining module. The referencesignaling configuration may pertain to reference signaling to bereceived by the receiving node.

Alternatively, or additionally, there may be envisioned:

There may be generally considered a radio node for a wirelesscommunication network and/or RAN, the radio node being adapted forreceiving and/or transmitting PT-RS based on any of the patternsdescribed herein. The radio node may comprise correspondingly adaptedreceiving and/or transmitting circuitry, and/or a correspondingtransmitting or receiving module. A method for operating a radio nodefor a wireless communication network and/or RAN may be considered. Themethod may comprise receiving and/or transmitting PT-RS based on any ofthe patterns described herein. The radio node may be a terminal or anetwork node. Receiving and/or transmitting may be based on a referencesignaling configuration, in particular a PT-RS configuration.

Receiving reference signaling may generally comprise evaluatingreference signaling based on the reference signaling configurationand/or using reference signaling for handling received signalingassociated to the reference signaling. Handling and/or evaluating maycomprise measuring the RS, and/or decoding and/or demodulating signalingbased on the RS and/or measurement of the RS. The receiving node maycomprise an evaluating module for such evaluating, and/or controlcircuitry and/or radio circuitry may be adapted for such evaluating. Inparticular, radio circuitry (in particular, receiving circuitry) maycomprise and/or be connected or connectable to measurement circuitry forcorresponding measurements. It may generally be considered thatreceiving comprises and/or based on the reference signalingconfiguration is based on the assumption that the RS configurationidentifies which parts of signaling are to be considered referencesignaling, in particular PT-RS.

Signaling associated to reference signaling may be signaling transmittedor received in the same resource block and/or TTI (Transmission TimeInterval) and/or subframe, and/or signaling to be decoded and/ordemodulated based on the reference signaling. The signaling associatedto reference signaling may occupy resources according to a prescriptionof the standard, which may identify which resources/signaling are to behandled based on which reference signaling. It may be considered thatfor each subcarrier in a carrier and/or resource block and/or subframeand/or TTI, there is one associated PT-RS on this subcarrier, such thatsignaling on resources associated to this subcarrier are handled basedon this PT-RS signal.

A receiving node may generally be a radio node, in particular, aterminal. However, in some cases, in particular for networks adapted forterminals transmitting UL in OFDM (as opposed to DFT-OFDM), a receivingnode may be a network node.

The reference signaling configuration may generally be a PT-RSconfiguration.

A reference signaling configuration (RS configuration), in particular aPT-RS configuration, generally may identify and/or described thereference signaling used, e.g. in terms of resources and/or distributionor pattern of signals over time/frequency, e.g., over a subframe and/orTTI, and/or related power and/or modulation. A reference signalingconfiguration may be indicated (e.g., explicitly) by one or moreindicators, which may be transmitted in a control message, and forexample indicate directly, and/or or index the configuration to a RSconfiguration table. Alternatively, or additionally, the RSconfiguration may be indicated by indication/s of one or moretransmission parameters (e.g., in a control message). In this case,there may be defined a (e.g., unique) mapping of the one or moretransmission parameters to a reference signaling, e.g. in a suitabletable or function. Such mapping may be available at and/or implementedat a transmitting node and/or a receiving node. A RS configuration mayindicate that no reference signaling of a specific kind, in particularPT-RS, is used, e.g. for a specific MCS. A RS configuration may be validas long as the transmission parameter/s it is based on are valid and/orused.

Transmission parameters may generally describe characteristics oftransmission, in particular physical characteristics. Transmissionparameters may include parameters indicating modulation and/or coding,in particular a Modulation and Coding Scheme (MCS). The number of bitsencoded in phase space, e.g. using QAM, may be seen as a transmissionparameter. Transmission parameters may comprise frequency (or frequencyrange of transmission, e.g. carrier and/or subcarriers used and/orbandwidth). It may be considered that transmission parameters compriseresources, in particular time/frequency resources, e.g. scheduledresources. In some variants, transmission parameters may comprise arelation (e.g., ratio) between expected ICI and expected CPE. It may beconsidered that transmission parameters may comprise MIMO layer and/ortransmission rank and/or parameters describing beam formingconfiguration, e.g. precoding and/or beam form (e.g., width and/orelevation). Transmission parameters may include scheduling information,in particular pertaining to other reference signaling to be transmitted,e.g. DM-RS.

A transmitting node may be a radio node, e.g. a network node. Thetransmitting may be in DL, and/or utilise OFDM. However, thetransmitting node may in some cases be a terminal, which may transmit inUL and/or utilise OFDM or SC-FDM.

A control message may be a message comprising control information and/orscheduling information (e.g., representing resources scheduled), and/orindication/s of one or more transmission parameters. A control messagemay be a radio or physical layer message. It may be considered that acontrol message transmitted in UL is a UCI message (Uplink ControlInformation). A control message transmitted in downlink may be a DCImessage (Downlink Control Information). Such messages may be accordingto a standard, e.g. a 3GPP standard like NR, and/or associated to theRAN utilised.

The term “dynamic” or similar terms may generally pertain toconfiguration/transmission valid and/or scheduled and/or configured for(relatively) short timescales and/or a (e.g., predefined and/orconfigured and/or limited and/or definite) number of occurrences and/ortransmission timing structures, e.g. one or more transmission timingstructures like slots or slot aggregations, and/or for one or more(e.g., specific number) of transmission/occurrences. Dynamicconfiguration may be based on low-level signaling, e.g. controlsignaling on the physical layer and/or MAC layer, in particular in theform of DCI. Periodic/semi-static may pertain to longer timescales, e.g.several slots and/or more than one frame, and/or a non-defined number ofoccurrences, e.g., until a dynamic configuration contradicts, or until anew periodic configuration arrives. A periodic or semi-staticconfiguration may be based on, and/or be configured with, higher-layersignaling, in particular RCL layer signaling and/or RRC signaling and/orMAC signaling.

Link adaptation generally may be considered to describe the adapting theMCS to operational conditions, e.g. based on interference, signalquality, signal-to noise or similar.

The reference signaling may comprise PT-RS and/or corresponding signals.

Generally, reference signaling, and/or a RS configuration, may beaccording to any of the approaches or proposals described herein, inparticular regarding the pattern and/or resources to be used for RS.

In the following, the term “user equipment”, or UE, may be considered arepresentation of the term “terminal”, and these terms may beinterchanged.

Precoding may refer to applying amplitude and/or phase shifts on each ofthe multiple antennas transmitting a signal, e.g. for beamforming. Suchprecoding may be based on and/or utilise a codebook, which mayprecoders, which may be pre-defined or alternatively dynamicallydefined, and/or a codebook may comprise a combination thereof.

As an example for the MCS dependent solution, in the basic case for afirst range MCS 0 . . . n no PT-RS is configured, and for a second rangeMCS n+1 . . . N there is an PT-RS configured with a pre-determined orsemi-statically configured frequency density, as depicted in FIG. 5.Accordingly, for a set of MCS selectable, for a first subset, PT-RS maybe indicated to not be transmitted (e.g., 0 . . . n), and for a secondsubset, PT-RS may be indicated to be transmitted (e.g., n+1 . . . N).The set may be indicated to have (monotonous, or strict monotonous)increase in modulation order for higher n. Generally, an MCS may beindicated by a number and/or parameter, e.g. indexing a table. In somevariants, the MCS indication may be adapted to indicate and/or select,multiple (at least two) MCS of the same type, e.g. with differentassociated and/or indicated PT-RS configurations, e.g. no PT-RS, PT-RSor different resource distributions and/or PT-RS densities selectable orindicatable for the MCS type. Such multiple MCS may be for one or moreMCS types.

An MCS type may indicate the modulation to be used and/or the order ofmodulation. Examples of MCS types comprise BPSK, QPSK, QAM, e.g., I-QAM,with I for example 4 or 8 or 16 or 32 or 64 or 128 or 256, etc. High MCSmay refer to an MCS type of a high order, e.g. 32 or more, low MCS mayrefer to an MCS type of low order, e.g. lower than 32. A comparison ofhigh MCS with low MCS may generally be considered to imply that the highMCS is of higher order than the low MCS.

An algorithm for implementation may comprise actions as shown in FIG. 6.

In an action S10, a control message like a DCI message may be receivedby a transmitting node like a terminal, respectively the message, and/orthe associated control information, may be determined and/or transmittedby a receiving node like a network node. The control message or DCI mayinclude an MCS indication. Optionally, it may indicate resources, e.g.time/frequency resources, for transmission, e.g. of data or controlinformation, e.g. on a PUSCH and/or PUCCH. The resources may beindicated as a resource set, e.g. with a resource indication. In anoptional action S12, a carrier frequency for the transmission may bedetermined and/or radio circuitry may be set (or kept) for transmissionon the carrier frequency, e.g. based on stored information and/or aconfiguration, which may be static and/or semi-static. In an action S14,a PT-RS mapping may be determined. The mapping may indicate on whichresources, e.g. of the resource set, the PT-RS are to be transmitted.The mapping may be determined based on the MCS indicated and theresource set and carrier frequency. A receiving node may perform anaction S16A, of reception of signaling based on the mapping. Thereception may comprise receiving considering the PT-RS mapping andtime-delay, e.g. due to signal traveling time between transmitter andreceiver. A transmitting node may perform an action S16B of transmissionbased on the PT-RS mapping, e.g. transmitting signaling including PT-RS.There may be considered a receiving node adapted for performing theactions associated to it. A transmitting node adapted for performing theactions associated to it may also be considered.

For an exemplary variant, a clear distinction for the MCS may beprovided, i.e. the MCS table will extend the usage of PT-RS to lower andlower MCS as the carrier frequency is increasing, as depicted in FIG. 7.

In some variants, multiple different densities of PT-RS may beconsidered, as exemplarily discussed herein. In some cases, MCS with andwithout PT-RS may be interlaced, e.g. MCS indicated 0 . . . 4, 6, 8 useno PT-RS, but MCS 5, 7, 9 . . . N use PT-RS.

Likewise, the presence of PT-RS may depend on the number of scheduledMIMO layers to the UE. In one variant, PT-RS is present only when morethan one layer is scheduled. In another variant, PT-RS may be presentwhen a combination criteria using MCS and number of layers are bothfulfilled. For instance, for high MCS and single layer, PT-RS may bepresent, and for multiple layers for any MCS it also may be present.

In another variant related to number of layers, multiple differentdensities of PT-RS may be defined, and the applicable density may dependon the number of scheduled layers.

A variant may consider PT-RS for CPE and extended PT-RS for CPE and ICIcorrection.

In some variants, there may be target scenarios where the carrierfrequency is sufficiently high such that it is not sufficient to correctCPE, but rather more extensive phase noise compensation would be needed.ICI may produce a significant degradation of SIR at very highfrequencies, and tends to increase strongly with increasing frequency.This implies that not only the common phase error needs correction, butrather correction is needed within one OFDM symbol to avoid excessiveICI. The approach could then still depend on MCS, but configuredifferent PT-RS resource mappings. For example, for low MCS, use of noPT-RS may be indicated, for middle MCS, use of PT-RS sufficient for CPEcompensation may be indicated, and for high MCS, use of an extendedPT-RS resource configuration may be indicated, that enables compensatingphase noise within the OFDM symbol, hence also mitigating the ICI.

A variant with MCS values for coverage using DFT-S-OFDM (which is alsoreferred to as SC-FDM herein) in UL is discussed. NR will support bothCP-OFDM and DFT-S-OFDM waveforms in UL. DFT-S-OFDM can be used, e.g., toachieve improved UL coverage when needed. The much lower peak-to-averagepower ratio (PAPR) of DFT-S-OFDM in comparison to CP-OFDM results inpotentially higher average UE output power. One implication ofDFT-S-OFDM is that reference signals should be time-multiplexed withphysical layer channels to preserve low PAPR. Since CPE is changing perOFDM symbol, there is a complication of using PT-RS in the case ofDFT-S-OFDM. This implies in some variants that some of the low MCSvalues may be used for better coverage and utilize DFT-S-OFDM, whereashigher MCS values may be used for data-rates and spectral efficiency.Hence, in some variants the coverage MCS are associated with DFT-S-OFDM,and in these cases no resources may be indicated or reserved for PT-RStransmissions.

It can be noticed that some low MCS values are potentially mapped toCP-OFDM and hence can have configured PT-RS. This is due to that in somecases low SINR can be targeted due to high interference rather than badcoverage.

A variant with muting resource elements to avoid interference isconsidered. In some variants, the overhead from PT-RS is not (or notonly) in the number of resource elements required, but rather due to theinterference caused to co-scheduled users. For example, in MU-MIMOscenarios were some users are using high MCS and some low MCS, then thelow MCS users can be muted in the PT-RS resource elements for the “NoPT-RS” case, as depicted in FIG. 8.

For low SINR, the addition of the phase noise may be drowned by theimpact of the noise and interference, hence compensating for the phasenoise may have little or no effect. Further, for the particular case ofCPE, the addition of a phase error is more severe for higher modulationschemes. Hence in cases with small or no benefit with PT-RS and phasenoise compensation, the PT-RS may be unnecessary overhead, potentiallymaking performance worse. In some scenarios, it may even be prohibitedto use PT-RS, e.g. for some DFT-S-OFDM variants.

There may be considered a method for signalling a PT-RS configuration ina DCI to a UE, where the UE receives, including at least an MCS or MCSindication, the number of MIMO layers and a resource mapping. The methodmay comprise

-   -   Determining a carrier frequency associated to said DCI;    -   Derive a PT-RS mapping from said DCI and carrier frequency;    -   Perform radio communication using said derived PT-RS mapping.

It is generally proposed to dynamically adopt the PT-RS in relation tothe transmission format, thus avoiding overhead either in term of lostdata elements or in terms of unnecessary interference too high SINRusers needing good CPE estimates.

Alternatively, or additionally to the above, there may be considered thefollowing:

Phase noise is present in any practical communication system, and impactthe system by introducing random phase variations of the receivedsignal. For an OFDM system, this will lead to inter-carrier interferenceas well as to a common phase error (CPE) on all subcarriers. Withincreasing carrier frequency, the variance of the phase noise increases,leading more pronounced problems. For NR, targeting carrier frequenciesof 6 GHz and above, measures need to be taken to reduce phase noiseinduced degradation of system performance.

In the following, design aspects of PT-RS are discussed.

Phase noise introduces both common phase errors (CPE) on allsubcarriers, which lead to a rotation of the received constellationsymbol, as well as inter carrier interference (ICI). The CPE is observedto dominate over the ICI introduced by phase noise. Therefore, thediscussion will mainly focus on using the PT-RS for CPE estimation. Itshould also be mentioned that PT-RS could also be used for frequencyoffset estimation.

It has been observed that lower order modulation is less sensitive tophase errors, as compared to higher order modulation. It is thereforeexpected that the problem with CPE will be more pronounced for users infavourable channel conditions, achieving the high SNR required forhigher order modulation. Therefore, PT-RS is not necessarily required tobe transmitted to/from all active UEs. From a resource utilizationperspective, it is therefore beneficial to only transmit PT-RS whenneeded. This will reduce overhead for the UL, and for DL if UE specificPT-RS are used, and interference in the case of shared PT-RS in DL.

Observation 1: PT-RS will mainly be needed for UEs scheduled for higher

order modulation, excluding UEs in unfavourable channel conditions.

Observation 2: Transmitting PT-RS only when needed may reduce overhead

and interference.

From the perspective of PT-RS, the UL and DL differs in a distinct way.In the UL, the received signals from different UEs are affected byindividual phase noise processes. The different UEs are thereforerequired to transmit independent PT-RS. For the DL, the PT-RS canpotentially be shared between all UEs being served by a single TRP(Transmission Point). This may be beneficial from a resource utilizationperspective, since resources are shared amongst UEs. Furthermore, ifdesigned properly, the PT-RS could be used for granular phase noisetracking used for ISI mitigation. On the other hand, since all UEs aretargeted with the PT-RS, UE specific beamforming cannot be used, thusreducing the coverage of the signal, unless other means are taken. Thistype of always-on signal also adds to the inter-site interference.Further on, a shared PT-RS also introduces an asymmetry in the design ofthe UL and DL. An alternative is instead to schedule UE specific PT-RS,which allows for beamforming and thus providing improved coverage.

Observation 3: For DL, the PT-RS can either be shared or UE specific,both having a number of implications requiring further study.

In the following subsection, discussions on the implications of UEspecific PT-RS in UL and DL is discussed.

Design considerations for UL PT-RS and UE specific PT-RS in DL arepresented in the following.

PT-RS can either be a standalone signal, or being co-scheduled withDM-RS. Irrespective of the approach taken, due to the short coherencetime of the phase noise, PT-RS may be needed to be transmitted on everyOFDM symbol in a subframe. At the same time, CPE may vary slow enough toallow for accurate interpolation.

Observation 4: PT-RS could potentially be transmitted more sparsely thatin every OFDM symbol.

An illustration of PT-RS placements is shown in FIG. 9. Note that theintersection between DM-RS and PT-RS has to be taken into account whendesigning the signal. It is important to preserve the orthogonalproperties of the DM-RS, as well as preserving the available channelestimation processing gain of a continuous DM-RS allocation.

Observation 5: PT-RS should be designed and placed in such a way that itdoes not impact the DM-RS related processing negatively.

It may be considered letting the values for the resource elements of thePT-RS on a given subcarrier, take on the value of the DM-RS on the samesubcarrier. That is, the PT-RS is obtained by repeating the DM-RS on thesubcarriers on which PT-RS is present.

Proposal 1: On a given subcarrier, the PT-RS should be formed by

repeating the value of the DM-RS on that subcarrier.

If designed to be a standalone signal, PT-RS well localized in frequencyis preferred, potentially covering one or several PRBs (PhysicalResource Blocks). This confinement provides a processing gain whenestimating the channel, needed for tracking the CPE over time. This alsohas the benefit of allowing the PT-RS to be transmitted withoutprecoding, enabling sharing between users in certain scenarios. Thechannel estimate obtained from DM-RS could be used to improve CPEestimation performance in certain scenarios. A downside of a frequencyconfined signal is that it is more sensitive to frequency selectivefading, as compared to a signal distributed in frequency.

By instead distributing the signal over a number of subcarriers, adiversity gain is achieved. This construction requires the PT-RS to relyon DM-RS, since an initial channel estimate is needed in order toestimate the CPE component. A benefit of this approach is that the DM-RSbased channel estimate will provide a reliable reference point due to,in general, a large processing gain. How many subcarriers are needed forPT-RS, and their placement in the scheduled resources, may depend on thelink quality, as well as on the scheduled bandwidth. An additionalaspect to consider is how to distribute PT-RS in frequency for differentsubcarrier spacing. Preferably, the placement should be numerologyindependent. The placement and density in frequency has to be furtherstudied.

Observation 6: The PT-RS can either be a standalone signal, or beco-scheduled with a DM-RS.

Observation 7: Placement in frequency can be made transparent to thenumerology, i.e., same PT-RS subcarrier distance, irrespective ofsubcarrier spacing.

For MIMO transmissions, the question arises on which Tx port to use forPT-RS transmission. Since the CPE can be approximated as common to allTx ports, transmitting the PT-RS on a single port could be sufficient.But such construction may have implications on the power density of thesignal, etc.

For co-scheduled UE transmissions in the UL, within the sametime-frequency resources, e.g. MU-MIMO, inter-UE interference has to beaddressed. Preferably, the PT-RS could be designed to allow for a numberof orthogonal signals. Due to the short coherence time of phase noise,applying coding in the time domain may not be a suitable option, insteadthe frequency domain need to be exploited for orthogonality.Additionally, when co-scheduling larger number of users, spatialseparation of UEs should instead be applied, as well as the use ofinterference cancellation in the receiver. This puts requirements onwhich receiver type to be assumed for evaluations of PT-RS dimensioning.

Observation 8: For co-scheduling users within the same time-frequencyresources in the UL, either orthogonal PT-RS signals could betransmitted, or spatial UE separation as well as interference cancellingreceivers could be exploited.

Based on the above discussion, the following proposals are made, whichmay be implemented independently or in any combination:

Proposal 2: As a baseline, PT-RS should be transmitted only when needed.

Proposal 3: As a baseline, the PT-RS should be configurable per UE.

Proposal 4: As a baseline, the PT-RS should be transmitted together withDM-RS.

Proposal 5: Study the required PT-RS time and frequency allocation withrespect to overhead and system performance.

Proposal 6: One orthogonal PT-RS for every four DM-RS ports should besufficient to handle, e.g. MU-MIMO.

Proposal 7: Receiver capabilities in terms of number of Rx antennabranches and interference suppression capabilities need to be taken intoaccount when dimensioning PT-RS.

Alternatively, or additionally, the following may be considered:

DL and UL CPE compensation in MIMO is discussed in the following.

In NR for higher carrier frequencies it is agreed that 3GPP should studythe effect of phase noise. In terms of phase noise, the main focus is tointroduce Phase Noise Compensation reference signals (PT-RS) tocompensate for common phase error (CPE) which constitutes thesignificant part of the phase noise. When evaluating CPE-compensation,the target is to have sufficient quality estimates of the CPE fordifferent deployment scenarios while maintaining a low overhead.

CPE compensation is more important for higher SINR and highermodulation, hence is targeted for higher bit-rate scenarios where it canbe assumed that the UE is more capable in terms of receiver and numberof RX/TX chains. Higher SINR is also suitable for higher order spatialmultiplexing, hence evaluation assumptions for MIMO evaluations shouldbe considered.

In higher frequencies, the smaller antennas elements sizes imply thatmore antenna elements can be fitted for a given area. Some of these willneed to be utilized to combat path-loss. But in many scenarios, e.g.hot-spot traffic off-load scenario, more RX/TX chains can also be addedcompared to typical LTE scenarios. In the receiver, there is apossibility to utilize this higher number of active RX branches to allowfor higher order spatial multiplexing in such hot-spot scenarios. Forthe UL, a larger number of uncorrelated TX phase noise components for ULMU-MIMO can scale the required number of orthogonal PT-RS signals in UL.Hence the overhead increases at least in terms of the radio interface ifthe resources are semi-statically assigned, but potentially also in thesignaling overhead if dynamically assigning the resource mappings. Thereceiver assumptions for the evaluations to investigate the PT-RSstructure to enable support for multiple TX-chains with uncorrelatedphase noise are discussed, e.g. for MU-MIMO in UL. Observe that somelarger set of PT-RS can be needed in DL for MU-MIMO also due to thatbeam-forming the PT-RS differently to different users may be considered.

To facilitate CPE estimation on PT-RS it is assumed here that PT-RS isgenerally not interfered by data from the same transmitter, e.g. due tocorresponding scheduling or configuration, which may generally hold forMIMO and/or non-MIMO cases. Furthermore, it is assumed that the PT-RS isbeam-formed to each receiver, e.g. UE-specific. Hence, in DL more userslead potentially to additional overhead, but the main focus here is ULMU-MIMO. When scaling the number of layers to the same user there is noneed for additional overhead for PT-RS. It is proposed that to exploitthis property, that is, each TX, when using multiple DM-RS ports to thesame user, only uses one of the assigned ports for transmitting thePT-RS. At the same time, data on the PT-RS resources for the other portsare muted. Further users with poor channel conditions and low SINR couldpotentially not need any PT-RS hence blanking all layers on the PT-RSresources as they are not in need of the CPE compensation may beconsidered. This is an approach to lower overhead in the MIMO case, andis one option to lower overhead that should be considered. Observe thatin the case when spatial multiplexing on data and then a lower orderspatial multiplexing of a set of PT-RS are used, this should give thesame or better quality on the PT-RS. Further, by sending the PT-RS overone of the DM-RS ports, the channel estimation and spatial interferencefiltering derived from the DM-RS can be reused for PT-RS receptionwithout needing to estimate this on the PT-RS signal.

Observation 1A: Sending PT-RS over one DM-RS port allows the receiver tocalculate spatial processing on DM-RS and reused this for PT-RSreception.

This is attractive from an overhead point of view, but may also affectthe CPE estimation. In particular, for both the frequency and the codemultiplexing of DM-RS this solution can have power density impact forthe PT-RS as depicted in FIG. 10.

Observation 2A: When using one of a multiple of TX ports the powerspectral density on the PT-RS can become lower than other resourceelements.

This lower power density could be adjusted, e.g. blanking adjacent dataresources to redistribute power, but such a solution then costsoverhead. But there is also a benefit if all transmitters are using thesame sub-carrier mapping for the PT-RS as a lower power density impliesthat a matching lower level of interference power is experienced on thePT-RS.

Observation 3A: Using a matching mapping of PT-RS between interferingtransmitters can lower the interference power on PT-RS.

Observation 4A: The experienced SINR on PT-RS will be the same or higherthan the SINR on the data symbols if spatially multiplexed PT-RS usesonly one out of a set of TX ports.

Continuing, the rank of the interference on PT-RS will be lower than therank of the interference on data resource elements. Hence the multipleset of RX-chains in the receiver can effectively be used for spatialinterference suppression techniques and improve estimation quality ofthe CPE further.

Observation 5A: Spatial interference suppression techniques will beimportant and effective on PT-RS.

From this discussion, we see that for PT-RS evaluations in UL MU-MIMOthere is a significant difference pertaining to two different 8×8 MIMOcases, either with 8 UEs with rank 1, or 2 UEs with rank 4 each, wherethe second case is much easier for high quality CPE estimation. Hencefor dimensioning PT-RS, the number of multiplexed UEs may be limited fora fixed number of receiver chains to not over-dimension the PT-RSresources.

In the case of one or a few dominating interferers, knowing the DM-RS toPT-RS mapping for the interferers would cater for more effective spatialinterference suppression, but potentially also interference cancellationon PT-RS if the interfering PT-RS symbols are known.

Observation 6A: Interference suppression/cancellation techniques couldbe even more effective if the receiver has knowledge about theinterfering PT-RS and DM-RS and interference is from PT-RS.

In case of uplink reception in MU-MIMO, a significant number of UE canpotentially be spatially multiplexed. Each such UE will have independentphase noise, and hence needs separate PT-RS. A concern is hence that thePT-RS overhead in UL can be significant. But from previous observations,and that the receiver in UL knows the DM-RS and PT-RS mapping for atleast all the users received in the same node, spatial processing cansignificantly lower the overhead needed for PT-RS. The dimensioning ofthe PT-RS in uplink is hence strongly dependent upon the number ofMU-MIMO users assumed in evaluations in relation to the number ofreceiver chains used for interference suppression/cancelation, inparticular if the receiver is capable of efficiently performing spatialseparation of the users.

Observation 7A: Dimensioning of PT-RS in UL is strongly dependent uponthe number of multiplexed users in relation to the number of receiverRX-chains used for interference suppression/cancelation.

This leads to the fact that in order to agree on PT-RS dimensioning inMU-MIMO, the evaluation assumptions must be agreed upon with respect tothe interference suppression/rejection techniques, and the number ofreceiver chains in relation to the number of PT-RS. From theseobservations the following proposals for PT-RS evaluations in MIMOscenarios may be considered, either independently or in any combination:

Proposal 1A: Consider PT-RS overhead reduction options by considering

spatial multiplexing and processing on PT-RS assuming the same resourcemapping for interfering PT-RS.

Proposal 2A: Consider the need for and options for maintaining goodpower

density on PT-RS without additional overhead.

Proposal 3A: As a baseline assume that spatial interference suppression

is used on PT-RS both in UL and DL.

Proposal 4A: As a baseline assume that a CPE compensation capable UE

has at least 2 receiver chains on orthogonal polarizations.

Proposal 5A: As a baseline assume that a BS has at least 2 receiverchains

on orthogonal polarizations in SU-MIMO.

Proposal 6A: As a baseline assume that a BS has at least 4 times thenumber of receiver chains than the number of users multiplex in ULMU-MIMO.

Possible PT-RS overhead reduction options are discussed. In particular,using one out of a multiple DM-RS ports for PT-RS in MIMO transmissionis considered. Further, the spatial processing on PT-RS to get a commonunderstanding on the needed overhead is considered.

FIG. 11 schematically shows a radio node or terminal 10, which may beimplemented in this example as a user equipment. Terminal 10 comprisescontrol circuitry 20, which may comprise a controller connected to amemory. Any module of the terminal, e.g. receiving module and/ortransmitting module and/or decoding module, may be implemented in and/orexecutable by the terminal, in particular the control circuitry 20, inparticular as module in the controller. Terminal 10 also comprises radiocircuitry 22 providing receiving and transmitting or transceivingfunctionality, the radio circuitry 22 (operably, e.g. to be controlledby the control circuitry) connected or connectable to the controlcircuitry. An antenna circuitry 24 of the terminal 10 is connected orconnectable to the radio circuitry 22 to receive or collect or sendand/or amplify signals. Radio circuitry 22 and the control circuitry 20controlling it may be adapted for receiving and/or transmittingreference signaling as disclosed herein. The terminal 10 may be adaptedto carry out any of the methods for operating a terminal disclosedherein; in particular, it may comprise corresponding circuitry, e.g.control circuitry.

FIG. 12 shows an exemplary radio node 100, which may be implemented as anetwork node. Radio node 100 comprises control circuitry 120, which maycomprise a controller connected to a memory. Any module, e.g. receivingmodule and/or transmitting module and/or configuring module (e.g., forconfiguring a terminal) of the radio node may be implemented in and/orexecutable by the control circuitry 120. The control circuitry 120 isconnected to control radio circuitry 122 of the network node 100, whichprovides receiver and transmitter and/or transceiver functionality. Anantenna circuitry 124 may be connected or connectable to radio circuitry122 for signal reception or transmittance and/or amplification. Theradio node 100 may be adapted to carry out any of the methods foroperating a radio node or network node disclosed herein; in particular,it may comprise corresponding circuitry, e.g. control circuitry. Theantenna circuitry may be connected to and/or comprise an antenna array.

In the context of this description, a receiving node, also sometimesreferred to as receiver, may be a terminal or node or device receivingreference signaling, e.g. PT-RS. A transmitting node, also sometimesreferred to a transmitter, may be a terminal or node or devicetransmitting reference signaling, e.g. PT-RS. It should be noted thattransmitter and receiver are also sometimes used to described radiocircuitry, e.g. as TX or RX or in the context of TX or RX chains. Themeaning of these terms while be clear from the context for a personskilled in the art.

Transmitting circuitry may be implemented as, and/or comprise, one ormore transmitters. Receiving circuitry may be implemented as, and/orcomprise, one or more receivers. Radio circuitry may comprise and/or beimplemented as transmitting circuitry and/or receiving circuitry.

There may be considered a radio node or network node adapted forperforming any one of the methods for operating a network node describedherein.

There may be considered a terminal or user equipment adapted forperforming any one of the methods for operating a radio node or terminaldescribed herein.

There is also disclosed a program product comprising code executable bycontrol circuitry, the code causing the control circuitry to carry outand/or control any one of the method for operating a radio node asdescribed herein, in particular if executed on control circuitry, whichmay be control circuitry of a user equipment or a network node.

Moreover, there is disclosed a carrier (or storage) medium arrangementcarrying and/or storing at least any one of the program productsdescribed herein and/or code executable by control circuitry, the codecausing the control circuitry to perform and/or control at least any oneof the methods described herein. A carrier medium arrangement maycomprise one or more carrier media. Generally, a carrier medium may beaccessible and/or readable and/or receivable by control circuitry.Storing data and/or a program product and/or code may be seen as part ofcarrying data and/or a program product and/or code. A carrier mediumgenerally may comprise a guiding/transporting medium and/or a storagemedium. A guiding/transporting medium may be adapted to carry and/orcarry and/or store signals, in particular electromagnetic signals and/orelectrical signals and/or magnetic signals and/or optical signals. Acarrier medium, in particular a guiding/transporting medium, may beadapted to guide such signals to carry them. A carrier medium, inparticular a guiding/transporting medium, may comprise theelectromagnetic field, e.g. radio waves or microwaves, and/or opticallytransmissive material, e.g. glass fiber, and/or cable. A storage mediummay comprise at least one of a memory, which may be volatile ornon-volatile, a buffer, a cache, an optical disc, magnetic memory, flashmemory, etc.

Resources may generally comprise time/frequency resources forcommunication, and/or associated power and/or codes, e.g. depending onthe multiplexing scheme used. References to resources, radio resourcesand/or time and/or frequency resources (e.g., subframe, slot, symbol orresource block) may refer to such resources structured according to 3GPP standards, in particular LTE and/or NR. It may be considered thatdecoding may comprise decoding of error detection coding and/or forwarderror coding. The extracted information may generally be and/or comprisecontrol information, in particular in a scheduling assignment. It may beconsidered that the extracted information is received on a controlchannel and/or is based on control channel signaling. Control channelsignaling may in particular be signaling on a physical control channel.

A terminal may be implemented as a user equipment. A terminal or a userequipment (UE) may generally be a device configured for wirelessdevice-to-device communication and/or a terminal for a wireless and/orcellular network, in particular a mobile terminal, for example a mobilephone, smart phone, tablet, PDA, etc. A user equipment or terminal maybe a node of or for a wireless communication network as describedherein, e.g. if it takes over some control and/or relay functionalityfor another terminal or node. It may be envisioned that terminal or auser equipment is adapted for one or more RATs, in particularLTE/E-UTRA. A terminal or user equipment may generally be proximityservices (ProSe) enabled, which may mean it is D2D capable or enabled.It may be considered that a terminal or user equipment comprises radiocircuitry and/control circuitry for wireless communication. Radiocircuitry may comprise for example a receiver device and/or transmitterdevice and/or transceiver device, and/or one or more receivers and/ortransmitters and/or transceivers. Control circuitry may include one ormore controllers, which may comprise a microprocessor and/ormicrocontroller and/or FPGA (Field-Programmable Gate Array) deviceand/or ASIC (Application Specific Integrated Circuit) device. It may beconsidered that control circuitry comprises or may be connected orconnectable to memory, which may be adapted to be accessible for readingand/or writing by the controller and/or control circuitry. It may beconsidered that a terminal or user equipment is configured to be aterminal or user equipment adapted for LTE/E-UTRAN. Reference signalingin the uplink may be associated to a terminal, e.g. SRS. A terminal mayin particular be adapted for V2x communication. A terminal may beadapted for one or more (cellular) Radio Access Technologies (RATs),e.g. LTE and/or UMTS and/or a 5G RAT, e.g. LTE Evolution and/or NR).Generally, a terminal may be any device adapted for wirelesscommunication via D2D and/or one or more cellular RATs. A wirelesscommunication network may comprise two or more terminals communicatingvia D2D communication, and/or a terminal communicating with a radioaccess node of a RAN (Radio Access Network) implementing one or moreRATs. Such a radio access node may e.g. be an eNodeB. It may generallybe considered that a terminal represents a device capable of serving asan end or termination point of a communication. A terminal may be a userequipment or phone or smart phone or computing device or sensor deviceor machine or vehicular device adapted for wireless communication asdescribed herein.

A radio node or network node or base station may be any kind of radionode or base station of a wireless and/or cellular network adapted toserve one or more terminals or user equipments. It may be consideredthat a base station is a node or network node of a wirelesscommunication network. A radio node or network node or base station maybe adapted to provide and/or define and/or to serve one or more cells ofthe network and/or to allocate frequency and/or time resources forcommunication to one or more nodes or terminals of a network. Generally,any node adapted to provide such functionality may be considered a basestation. It may be considered that a base station or more generally anetwork node, in particular a radio network node, comprises radiocircuitry and/or control circuitry for wireless communication. It may beenvisioned that a base station or radio node is adapted for one or moreRATs, in particular LTE/E-UTRA. Radio circuitry may comprise for examplea receiver device and/or transmitter device and/or transceiver device.Control circuitry may include one or more controllers, which maycomprise a microprocessor and/or microcontroller and/or FPGA(Field-Programmable Gate Array) device and/or ASIC (Application SpecificIntegrated Circuit) device. It may be considered that control circuitrycomprises or may be connected or connectable to memory, which may beadapted to be accessible for reading and/or writing by the controllerand/or control circuitry. A base station may be arranged to be a node ofa wireless communication network, in particular configured for and/or toenable and/or to facilitate and/or to participate in cellularcommunication, e.g. as a device directly involved or as an auxiliaryand/or coordinating node. Generally, a base station may be arranged tocommunicate with a core network and/or to provide services and/orcontrol to one or more user equipments and/or to relay and/or transportcommunications and/or data between one or more user equipments and acore network and/or another base station and/or be Proximity Serviceenabled.

A radio node, in particular a network node or a terminal, may generallybe any device adapted for transmitting and/or receiving radio and/orwireless signals and/or data, in particular communication data, inparticular on at least one carrier. A radio node may generally be anetwork node or a terminal and/or user equipment. A radio node may inparticular be a user equipment or a base station and/or relay nodeand/or micro-(or pico/femto/nano-)node of or for a network, e.g., aneNodeB or gNodeB. Transmission of data may be in uplink (UL) fortransmissions from a user equipment to a base station/node/network.Transmission of data may be considered in downlink (DL) for transmissionfrom a base station/node/network to a user equipment or terminal. Thetarget of transmission may generally be another radio node, inparticular a radio node as described herein.

An eNodeB (eNB) or gNodeB may be envisioned as an example of a radionode or network node or base station, e.g. according to an LTE standard.A radio node or base station may generally be proximity service enabledand/or to provide corresponding services. It may be considered that aradio node base station is configured as or connected or connectable toan Evolved Packet Core (EPC) and/or to provide and/or connect tocorresponding functionality. The functionality and/or multiple differentfunctions of a radio node or base station may be distributed over one ormore different devices and/or physical locations and/or nodes. A radionode or base station may be considered to be a node of a wirelesscommunication network. Generally, a radio node or base station may beconsidered to be configured to be a coordinating node and/or to allocateresources in particular for cellular communication between two nodes orterminals of a wireless communication network, in particular two userequipments.

Receiving or transmitting on a cell or carrier may refer to receiving ortransmitting utilizing a frequency (band) or spectrum associated to thecell or carrier. A cell may generally comprise and/or be defined by orfor one or more carriers, in particular at least one carrier for ULcommunication/transmission (called UL carrier) and at least one carrierfor DL communication/transmission (called DL carrier). It may beconsidered that a cell comprises different numbers of UL carriers and DLcarriers. Alternatively or additionally, a cell may comprise at leastone carrier for UL communication/transmission and DLcommunication/transmission, e.g., in TDD-based approaches.

A channel may generally be a logical or physical channel. A channel maycomprise and/or be arranged on one or more carriers, in particular aplurality of subcarriers.

A wireless communication network may comprise at least one network node,in particular a network node as described herein. A terminal connectedor communicating with a network may be considered to be connected orcommunicating with at least one network node, in particular any one ofthe network nodes described herein.

A cell may be generally a communication cell, e.g., of a cellular ormobile communication network, provided by a node. A serving cell may bea cell on or via which a network node (the node providing or associatedto the cell, e.g., base station or eNodeB) transmits and/or may transmitdata (which may be data other than broadcast data) to a user equipment,in particular control and/or user or payload data, and/or via or onwhich a user equipment transmits and/or may transmit data to the node; aserving cell may be a cell for or on which the user equipment isconfigured and/or to which it is synchronized and/or has performed anaccess procedure, e.g., a random access procedure, and/or in relation towhich it is in a RRC_connected or RRC_idle state, e.g., in case the nodeand/or user equipment and/or network follow the LTE-standard. One ormore carriers (e.g., uplink and/or downlink carrier/s and/or a carrierfor both uplink and downlink) may be associated to a cell.

It may be considered for cellular communication there is provided atleast one uplink (UL) connection and/or channel and/or carrier and atleast one downlink (DL) connection and/or channel and/or carrier, e.g.,via and/or defining a cell, which may be provided by a network node, inparticular a base station or eNodeB. An uplink direction may refer to adata transfer direction from a terminal to a network node, e.g., basestation and/or relay station. A downlink direction may refer to a datatransfer direction from a network node, e.g., base station and/or relaynode, to a terminal. UL and DL may be associated to different frequencyresources, e.g., carriers and/or spectral bands. A cell may comprise atleast one uplink carrier and at least one downlink carrier, which mayhave different frequency bands. A network node, e.g., a base station oreNodeB, may be adapted to provide and/or define and/or control one ormore cells, e.g., a PCell and/or a LA cell.

Configuring a terminal or wireless device or node may involveinstructing and/or causing the wireless device or node to change itsconfiguration, e.g., at least one setting and/or register entry and/oroperational mode. A terminal or wireless device or node may be adaptedto configure itself, e.g., according to information or data in a memoryof the terminal or wireless device. Configuring a node or terminal orwireless device by another device or node or a network may refer toand/or comprise transmitting information and/or data and/or instructionsto the wireless device or node by the other device or node or thenetwork, e.g., allocation data (which may also be and/or compriseconfiguration data) and/or scheduling data and/or scheduling grants.Configuring a terminal may include sending allocation/configuration datato the terminal indicating which modulation and/or encoding to use. Aterminal may be configured with and/or for scheduling data and/or touse, e.g., for transmission, scheduled and/or allocated uplinkresources, and/or, e.g., for reception, scheduled and/or allocateddownlink resources. Uplink resources and/or downlink resources may bescheduled and/or provided with allocation or configuration data.

Generally, control circuitry may comprise integrated circuitry forprocessing and/or control, e.g., one or more processors and/or processorcores and/or FPGAs (Field Programmable Gate Array) and/or ASICs(Application Specific Integrated Circuitry). Control circuitry maycomprise and/or be connected to and/or be adapted for accessing (e.g.,writing to and/or reading from) memory, which may comprise any kind ofvolatile and/or non-volatile memory, e.g., cache and/or buffer memoryand/or RAM (Random Access Memory) and/or ROM (Read-Only Memory) and/oroptical memory and/or EPROM (Erasable Programmable Read-Only Memory).Such memory may be adapted to store code executable by control circuitryand/or other data, e.g., data pertaining to communication, e.g.,configuration/s and/or address data of nodes, etc. Control circuitry maybe adapted to control any of the methods described herein and/or tocause such methods to be performed, e.g., by the radio node.Corresponding instructions may be stored in the memory, which may bereadable and/or readably connected to the control circuitry. Controlcircuitry may include a controller, which may comprise a microprocessorand/or microcontroller and/or FPGA (Field-Programmable Gate Array)device and/or ASIC (Application Specific Integrated Circuit) device. Itmay be considered that control circuitry comprises or may be connectedor connectable to memory, which may be adapted to be accessible forreading and/or writing by the controller and/or control circuitry.

Radio circuitry may comprise receiving circuitry (e.g., one or morereceivers) and/or transmitting circuitry (e.g., one or moretransmitters). Alternatively, or additionally, radio circuitry maycomprise transceiving circuitry for transmitting and receiving (e.g.,one or more transceivers). Radio circuitry may generally comprise, forexample, a receiver device and/or transmitter device and/or transceiverdevice.

Antenna circuitry may comprise one or more antennas or antenna elements,which may be arranged in an antenna array. It may be considered thatantenna circuitry comprises one or more additional elements and/or isconnected or connectable to one or more additional elements, e.g.,wiring.

Configuring a radio node, in particular a user equipment, may refer tothe radio node being adapted or caused or set to operate according tothe configuration. Configuring may be done by another device, e.g., anetwork node (for example, a radio node of the network like a basestation or eNodeB) or network, in which case it may comprisetransmitting configuration data to the radio node to be configured. Suchconfiguration data may represent the configuration to be configuredand/or comprise one or more instruction pertaining to a configuration,e.g., regarding a freeze interval and/or a transmission start interval.A radio node may configure itself, e.g., based on configuration datareceived from a network or network node.

Generally, configuring may include determining configuration datarepresenting the configuration and providing it to one or more othernodes (parallel and/or sequentially), which may transmit it further tothe radio node (or another node, which may be repeated until it reachesthe wireless device). Alternatively, or additionally, configuring aradio node, e.g., by a network node or other device, may includereceiving configuration data and/or data pertaining to configurationdata, e.g., from another node like a network node, which may be ahigher-level node of the network, and/or transmitting receivedconfiguration data to the radio node. Accordingly, determining aconfiguration and transmitting the configuration data to the radio nodemay be performed by different network nodes or entities, which may beable to communicate via a suitable interface, e.g., an X2 interface inthe case of LTE.

A carrier may comprise a continuous or discontinuous radio frequencybandwidth and/or frequency distribution, and/or may carry, and/or beutilized or utilizable for transmitting, information and/or signals, inparticular communication data. It may be considered that a carrier isdefined by and/or referred to and/or indexed according to for example astandard like LTE. A carrier may comprise one or more subcarriers. A setof subcarriers (comprising at least one subcarrier) may be referred toas carrier, e.g., if a common LBT procedure (e.g., measuring the totalenergy/power for the set) is performed for the set. A channel maycomprise at least one carrier. A channel may in particular be a physicalchannel and/or comprise and/or refer to a frequency range. Accessing acarrier or channel may comprise transmitting on the carrier. Ifaccessing a carrier or channel is allowed, this may indicate thattransmission on this carrier is allowed.

Signaling may comprise one or more signals and/or symbols. Referencesignaling may comprise one or more reference signals and/or symbols.Data signaling may pertain to signals and/or symbols containing data, inparticular user data and/or payload data and/or data from acommunication layer above the radio and/or physical layer/s. It may beconsidered that demodulation reference signaling comprises one or moredemodulation signals and/or symbols. Demodulation reference signalingmay in particular comprise DM-RS according to 3GPP and/or LTEtechnologies. Demodulation reference signaling may generally beconsidered to represent signaling providing reference for a receivingdevice like a terminal to decode and/or demodulate associated datasignaling or data. Demodulation reference signaling may be associated todata or data signaling, in particular to specific data or datasignaling. It may be considered that data signaling and demodulationreference signaling are interlaced and/or multiplexed, e.g. arranged inthe same time interval covering e.g. a subframe or slot or symbol,and/or in the same time-frequency resource structure like a resourceblock. A resource element may represent a smallest time-frequencyresource, e.g. representing the time and frequency range covered by onesymbol or a number of bits represented in a common modulation. Aresource element may e.g. cover a symbol time length and a subcarrier,in particular in 3GPP and/or LTE standards. A data transmission mayrepresent and/or pertain to transmission of specific data, e.g. aspecific block of data and/or transport block. Generally, demodulationreference signaling may comprise and/or represent a sequence of signalsand/or symbols, which may identify and/or define the demodulationreference signaling.

A channel may generally be a logical or physical channel. A channel maycomprise and/or be arranged on one or more carriers, in particular aplurality of subcarriers. A control channel may be such a channel. Acommunication may generally involve transmitting and/or receivingmessages, in particular in the form of packet data. A message or packetmay comprise control and/or configuration data and/or payload dataand/or represent and/or comprise a batch of physical layertransmissions. Control and/or configuration information or data mayrefer to data pertaining to the process of communication and/or nodesand/or terminals of the communication. It may, e.g., include addressdata referring to a node or terminal of the communication and/or datapertaining to the transmission mode and/or spectral configuration and/orfrequency and/or coding and/or timing and/or bandwidth as datapertaining to the process of communication or transmission, e.g. in aheader. Generally, a message may comprise one or more signals and/orsymbols.

Data may refer to any kind of data, in particular any one of and/or anycombination of control data or user data or payload data. Controlinformation (which may also be referred to as control data) may refer todata controlling and/or scheduling and/or pertaining to the process ofdata transmission and/or the network or terminal operation.

Terminal-specific (or UE-specific) transmission may be addressed and/orintended and/or encoded for a specific terminal or UE (or a groupthereof), e.g. by encoding and/or spreading with a correspondingidentification, e.g. a RNTI.

In this disclosure, for purposes of explanation and not limitation,specific details are set forth (such as particular network functions,processes and signaling steps) in order to provide a thoroughunderstanding of the technique presented herein. It will be apparent toone skilled in the art that the present concepts and aspects may bepracticed in other variants and variants that depart from these specificdetails.

For example, the concepts and variants are partially described in thecontext of Long Term Evolution (LTE) or LTE-Advanced (LTE-A) or NextRadio mobile or wireless communications technologies; however, this doesnot rule out the use of the present concepts and aspects in connectionwith additional or alternative mobile communication technologies such asthe Global System for Mobile Communications (GSM). While the followingvariants will partially be described with respect to certain TechnicalSpecifications (TSs) of the Third Generation Partnership Project (3GPP),it will be appreciated that the present concepts and aspects could alsobe realized in connection with different Performance Management (PM)specifications.

Moreover, those skilled in the art will appreciate that the services,functions and steps explained herein may be implemented using softwarefunctioning in conjunction with a programmed microprocessor, or using anApplication Specific Integrated Circuit (ASIC), a Digital SignalProcessor (DSP), a Field Programmable Gate Array (FPGA) or generalpurpose computer. It will also be appreciated that while the variantsdescribed herein are elucidated in the context of methods and devices,the concepts and aspects presented herein may also be embodied in aprogram product as well as in a system comprising control circuitry,e.g. a computer processor and a memory coupled to the processor, whereinthe memory is encoded with one or more programs or program products thatexecute the services, functions and steps disclosed herein.

It is believed that the advantages of the aspects and variants presentedherein will be fully understood from the foregoing description, and itwill be apparent that various changes may be made in the form,constructions and arrangement of the exemplary aspects thereof withoutdeparting from the scope of the concepts and aspects described herein orwithout sacrificing all of its advantageous effects. The aspectspresented herein can be varied in many ways.

Some useful abbreviations comprise:

-   3GPP Third Generation Partnership Project-   eNB Enhanced NodeB-   CRS Cell-Specific Reference Signal-   DM-RS De-Modulation Reference Signal-   DCI Downlink Control Information-   LTE Long Term Evolution-   MIMO Multiple Input Multiple Output-   MU Multi-user-   PT-RS Phase Tracking RS-   RS Reference Signal-   TM Transmission Mode-   TTI Transmission Time Interval-   UE User Equipment-   DL Downlink, pertaining to transmission from a network node to a    terminal-   UL Uplink, pertaining to transmission from a terminal to a network    node-   NR New Radio-   RNTI Radio Network Temporary Identifier

Transmission in the context of this disclosure may pertain to wirelesstransmission in a RAN.

What is claimed is:
 1. A method for operating a user equipment in a NewRadio (NR) Radio Access Network, the method comprising: transmittingPhase Tracking Reference Signaling (PT-RS) according to a time-frequencyresource distribution, wherein the time-frequency resource distributionof the PT-RS is based on a Modulation and Coding Scheme (MCS) indicationin a received Downlink Control Information (DCI) message, and ascheduled bandwidth indicated in the DCI message, the MCS indicationindicating an MCS to be used and the scheduled bandwidth representing aplurality of subcarriers to be used for transmission.
 2. The method ofclaim 1, wherein transmitting PT-RS uses an Orthogonal FrequencyDivision Multiplex-based waveform.
 3. The method of claim 1, wherein thescheduled bandwidth and the MCS pertain to transmission on a PhysicalUplink Shared Channel (PUSCH).
 4. The method of claim 1, wherein thetime-frequency resource distribution represents a time domaindistribution covering a plurality of symbols, wherein the PT-RS is notused on every symbol.
 5. The method of claim 1, wherein thetime-frequency resource distribution represents a frequency domaindistribution covering the scheduled bandwidth, wherein a number ofsubcarriers of the plurality of subcarriers of the scheduled bandwidthused for PT-RS and their placement among the plurality of subcarriers isdependent on the scheduled bandwidth.
 6. The method of claim 1, whereinthe MCS may be selected from a set of MCS by the indication, wherein fora first subset of the set of MCS, PT-RS is not used, and for a secondsubset, PT-RS is used.
 7. The method of claim 1, wherein the density ofPT-RS in frequency domain is dependent on the scheduled bandwidth.
 8. Auser equipment (UE) for a New Radio (NR) Radio Access Network, the userequipment comprising: control circuitry; and radio circuitry; whereinthe control circuitry and radio circuitry are configured to transmitPhase Tracking Reference Signaling (PT-RS) according to a time-frequencyresource distribution, wherein the time-frequency resource distributionof the PT-RS is based on a Modulation and Coding Scheme (MCS) indicationin a received Downlink Control Information (DCI) message, and ascheduled bandwidth indicated in the DCI message; the MCS indicationindicating an MCS to be used and the scheduled bandwidth representing aplurality of subcarriers to be used for transmission.
 9. The UE of claim8, wherein the control circuitry and radio circuitry are configured totransmit the PT-RS using an Orthogonal Frequency DivisionMultiplex-based waveform.
 10. The UE of claim 8, wherein the scheduledbandwidth and the MCS pertain to transmission on a Physical UplinkShared Channel (PUSCH).
 11. The UE of claim 8, wherein thetime-frequency resource distribution represents a time domaindistribution covering a plurality of symbols, wherein the PT-RS is notused on every symbol.
 12. The UE of claim 8, wherein the time-frequencyresource distribution represents a frequency domain distributioncovering the scheduled bandwidth, wherein a number of subcarriers of theplurality of subcarriers of the scheduled bandwidth used for PT-RS andtheir placement among the plurality of subcarriers is dependent on thescheduled bandwidth.
 13. The UE of claim 8, wherein the controlcircuitry and radio circuitry are configured to select the MCS from aset of MCS based on the indication, wherein for a first subset of theset of MCS, PT-RS is not used, and for a second subset, PT-RS is used.14. The UE of claim 8, wherein the density of PT-RS in frequency domainis dependent on the scheduled bandwidth.
 15. A network node for a NewRadio (NR) Radio Access Network, the network node comprising: controlcircuitry; and radio circuitry; wherein the control circuitry and radiocircuitry are configured to: transmit, to a user equipment, a DownlinkControl Information (DCI) message, the DCI message including aModulation and Coding Scheme indication indicating an MCS to be used fortransmission, the DCI message also indicating a scheduled bandwidth, thescheduled bandwidth representing a plurality of subcarriers to be usedfor transmission; and receive, from the user equipment, Phase TrackingReference Signaling (PT-RS) according to a time-frequency resourcedistribution, wherein the time-frequency resource distribution of thePT-RS is based on the Modulation and Coding Scheme (MCS) indication andthe scheduled bandwidth.
 16. The network node of claim 15, wherein thescheduled bandwidth and the MCS pertain to transmission on a PhysicalUplink Shared Channel (PUSCH).
 17. The network node of claim 15, whereinthe time-frequency resource distribution represents a time domaindistribution covering a plurality of symbols, wherein the PT-RS is notused on every symbol.
 18. The network node of claim 15, wherein thetime-frequency resource distribution represents a frequency domaindistribution covering the scheduled bandwidth, wherein a number ofsubcarriers of the plurality of subcarriers of the scheduled bandwidthused for PT-RS and their placement among the plurality of subcarriers isdependent on the scheduled bandwidth.
 19. The network node of claim 15,wherein the MCS may be selected from a set of MCS by the indication,wherein for a first subset of the set of MCS, PT-RS is not used, and fora second subset, PT-RS is used.
 20. The network node of claim 15,wherein the density of PT-RS in frequency domain is dependent on thescheduled bandwidth.